This invention relates to a ceramic article for use in supporting or mounting a semiconductor chip or chips and to a method of manufacturing the same. It is to be noted throughout the instant specification that the ceramic article comprises a ceramic body and a conductive pattern attached to the ceramic body.
Recent demands have been directed towards a ceramic article which is fired at a low temperature lower than 1600.degree. C., preferably lower than 1000.degree. C. and which may often be referred to as a low temperature firing ceramic article. Such a ceramic article dispenses as conductive patterns with use of tungsten, molybdenum, or the like, which has a high melting point and which is liable to oxidation. In other words, the conductive patterns may be formed in such a ceramic article by noble metal, such as gold, an alloy of silver and palladium, which has a high electrical conductivity. This means that a resistance of the conductive patterns can be reduced by the use of such a high conductivity metal. Therefore, the above article may be applied to a very high speed computer like a super computer.
In Unexamined Japanese Patent Publication No. 17,651/1983 by H. Tozaki et al, a ceramic article is disclosed which comprises a ceramic body produced from a composition comprising a nonconductive crystalline oxide material and a vitreous or amorphous material. The nonconductive crystalline oxide material may be selected from alumina (Al.sub.2 O.sub.3), silica (SiO.sub.2), magnesia (MgO), calcium oxide (CaO), barium oxide (BaO), zirconia (ZrO.sub.2), or the like. On the other hand, the vitreous material may be alumino and borosilicate lead glass. An alkali metal oxide, such as sodium oxide (Na.sub.2 O), lithium oxide (Li.sub.2 O), potassium oxide (K.sub.2 O), may be added to the vitreous material.
A conductive pattern of the noble metal may be attached to the above-mentioned ceramic body. A small amount of a vitreous material may be included in the conductive pattern in order to improve adhesion between the ceramic body and the conductive pattern.
At any rate, the ceramic body and the conductive pattern are simultaneously fired or cofired into the ceramic article. In this event, a resistor pattern and a capacitor pattern may be formed on the ceramic body together with the conductive pattern.
With this structure, the conductive pattern may be laid not only on a surface of the ceramic body but also inside of the ceramic body and is therefore divided into an external part and an internal part. The external and the internal parts are constituted by a common noble metal.
In the meanwhile, it has been found out that the above-mentioned ceramic article exhibits a low moisture proof on a moisture test when silver is used as the conductive patterns. As a result, migration and dielectric break down are liable to occur in the external part and in the ceramic body, respectively. The liability to migration and dielectric breakdown may be ascribed to presence of lead oxide and alkali metal oxide. Therefore, use of silver should be prohibited in the ceramic article.
Instead, gold or an alloy of silver and palladium must be attached as the conductive pattern to the ceramic body. However, the conductive pattern of gold makes the ceramic article expensive on one hand. On the other hand, the alloy of silver and palladium makes sheet resistances of the conductive patterns high. For example, the alloy of silver and palladium has a sheet resistance of 20 m.OMEGA./.quadrature. when it comprises by weight 80% silver and 20% palladium. Use of the silver and palladium alloy results in an inevitable reduction of electric characteristics of the article.